In the distributing industry, means of managing products (goods) are shifting from barcodes or the like to RFID (Radio Frequency Identification) using wireless chips or the like. The RFID is drawing attention as the important technique not only in promoting efficiency of stock and distribution of products but also in promoting the information technology and the automation technology, as wireless chips are added to various products in using the RFID. The RFID may be used for enabling a purchaser to search information on a food product he bought such as its producing region, its producer or its processor based on RFID data, or for a user to automatically list up foods stored in his refrigerator and notice him of expiration date of the foods. In order to put the RFID into widespread use, the RFID must be inexpensively supplied and used.
In order to inexpensively supply and use the RFID, the most feasible option of the RFID is that the RFID made to save only product identifying information such as ID information, with information on product such as the producer and tracking information of the distribution channel being recorded in a product database (DB) server or the like and referenced by the product ID information. Practically, product ID information is read through a tag reader, sent to the product DB server to enable information on the product information to be accessed. In such a case, an authorized owner of an authority must be assured to access the information and an abuser must be prevented from acquiring product information, from distributing fake products, or from interfering a traceability system with fake goods or the like.
The following documents are considered:    [Patent Document 1] National Publication of International Patent Application No. 2003-524242    [Patent Document 2] Published Unexamined Patent Application No. 2001-184312    [Patent Document 3] Published Unexamined Patent Application No. 2001-160177    [Patent Document 4] Published Unexamined Patent Application No. 2001-160177    [Non-patent Document 1] A. Juels and J. Brainard, “Soft Blocking: Flexible Blocker Tags on the Cheap,” URL: http://www.rsasecurity.com/rsalabs/staff/bios/ajuels/publica tions/softblocker/softblocker.pdf.
Patent Document 1 describes a method for providing a tag chip with two storage areas of a tag address and a security block and verifying a tag address usually read as RFID by comparing the tag with the second security block. A tag reader first reads a tag address, encrypts the tag address with a secret key it holds, and verifies the tag address by comparing the encrypted result and a value in the security block. Patent Document 2 discloses a method for saving verifying information in the tag and making a reader verify the owner with the authority by using the verifying information. This method saves information on a face image, a signature or a password in a tag for locally verifying the owner. Patent Document 2 shows a system for providing RFID to both a user and a confidential document and allowing a user to copy or the like the document only if the security level of the RFID owned by the user is higher than that of the RFID tag added to the confidential document. Patent Document 4 shows that a wireless tag stores goods identifiers and goods secret keys, creates goods digital signature by using the goods secret key or the like, and sends the goods digital signature to a verifying computer for verification. Non Patent Document 1 shows a method for controlling the reading of RFID added to a product with another RFID tag called Blocker tag by using a multi-accessing function of a reader.